The subject invention is directed to a breath analyzer which is capable of detecting toxic gas levels from breath analysis. The subject invention includes a mouthpiece which is in communication with a plurality of discrete chambers, such as first and second discrete chambers, each being provided with a separate probe for breath analysis. The probes are connected to analyzers for determining detected levels of gas. In a first embodiment, a first probe may be provided for carbon monoxide detection with a second probe being provided for hydrogen cyanide detection. Advantageously, with this arrangement, breath analysis may be conducted on-site, for example at the site of a fire, to quickly and simultaneously determine carbon monoxide and hydrogen cyanide levels in a person's blood stream. In a second embodiment, a first probe may be provided for detection of carbon monoxide and a second probe may be provided for detection of hydrogen. With this arrangement, a calibrated correction of measured carbon monoxide data can be made to correct for improperly detected hydrogen. As such, a highly accurate on-site measurement for carbon monoxide can be achieved.